1. Field of the Invention
This invention relates generally to a technique for force-fitting a separate member into a casting, and more particularly to such a technique for force-fitting the separate member into the casting while the casting is enclosed in a casting mold.
For example, when a cylinder block of an internal combustion engine having an internal cooling liquid passage is made by casting, a pipe is force-fitted into a casting so that a hose for supplying a cooling liquid to the cooling liquid passage is connected to the cylinder block through the pipe. Furthermore, there is known a technique in which a passage is formed in a casting, the passage being communicated with the outside of the casting at a hole formed at a surface of the casting, and later the hole is closed by force-fitting a separate member into the hole so that the passage closed at the surface of the casting is completed in the casting. The invention meets the above-described needs.
2. Description of the Prior Art
Generally, when a separate member is force-fitted into a casting, the casting is taken out from a casting mold, the taken out casting is cooled, the cooled casting is transferred to a subsequent stage where a force-fitting portion of the casting into which the separate member is to be force-fitted is machined so as to be suitable for the force-fitting, and finally the separate member is force-fitted into the machined portion of the casting. Furthermore, the force-fitting portion is externally caulked after the force-fitting when the caulking is necessary, so that the separate member is prevented from falling off therefrom.
The above-described prior art technique necessitates the machining and force-fitting steps as well as the casting step. As a result, the manufacture of the products requires an increased time and cost.
A force-fitting interference needs to be rendered sufficiently large in order that the separate member is reliably force-fitted into the casting. The force-fitting interference refers to the difference between the outer diameter of the separate member and the inner diameter of a concave portion of the casting into which the separate member is to be force-fitted. The casting tends to be cracked or deformed when the force-fitting interference is rendered large.